1. Field of the Invention
The present invention relates, generally, to photosensitive metal nanoparticles and methods of forming conductive patterns using the same. More specifically, the present invention relates to a photosenstivie metal nanoparticle, produced by forming a self-assembled monolayer of a thiol or isocyanide compound having a terminal reactive group on its surface and introducing a photosensitive group through the terminal reactive group; and a method of forming a conductive pattern using the same.
2. Description of the Related Art
Nano-sized materials, having various electrical, optical and biological properties depending on the orders and spatial structures of one-, two- and three-dimensions, have been earnestly researched for a variety of fields all over the world. Among various types of the nano-sized materials, metal nano-particle can be used widely for various applications because, when metal is reduced to nano-size from its bulk state, metal nano particle has extremely large surface while there are very few metal atoms in the particle, and for this reason, metal nano-particle exhibits unique catalytic, electrical, photoelectric and magnetic properties [Science, 256, 1425 (1992) and Colloid Polymer. Sci. 273, 101 (1995)]. Metal nanoparticles, showing conductivity through an electroconductive mechanism of charge (or electron) transfer, have such a large specific surface area that, even when small amounts of the nanoparticles are used, their film or pattern can exhibit high conductivity. In addition, if packing is made more densely by controlling a particle size within a range of 3-15 nm, a charge transfer at interfaces of metals can be carried out more easily, resulting in higher conductivity.
With great advances in electronic industries, many attempts have been made to develop highly conductive films or patterns using various materials. In this regard, it is expected that metal nano particle can produce a high conductive film or pattern without performing an etching or sputtering process requiring high vacuum and/or high temperatures. Once being realized, preparation of a conductive film by using metal nano particle will be very useful because the film thus obtained can be transparent under visible rays by controlling particle size. However, for metal nano particles to be used in a form of film or pattern, there remains difficulties to overcome, i.e. controlling and arraying such fine particles efficiently.
For efficient arrays of the metal nanoparticles, there are a few proposed methods of using a self-assembled monolayer. The self-assembled monolayer is a layer formed on a surface of metal nanoparticle by arraying molecules of a compound having a functional group with chemical affinity to a specific metal and, its thickness can be controlled to the nano-scale, for example, from 10 to 40 nm. Generally, molecules of a compound having an amino group (—NH2), an isocyanide group (—CN), or a thiol group (—SH) are arrayed on a nano-metal, such as gold, silver, copper, palladium, or platinum, to form a self-assembled monolayer [Chem. Rev. 96, 1533 (1996)].
However, in the case of using the self-assembled monolayer method, it is not easy to prepare metal nanoparticle films or patterns in a large size because of difficulty in controlling molecular orientation or spatial ordering, instability or aggregation of the metal nanoparticles in a thin film, and defects of film. For this reason, the metal nano particle or its film or pattern has been limited in their commercial application.
Therefore, in the art, there is a strong demand to develop a novel self-assembled nano structure that enables forming a large area film or pattern of the metal nanoparticles.